1. Field of the Invention
This invention relates to methods for fabricating electrochemical cells and more particularly to methods for fabricating high-temperature secondary electrochemical cells or batteries which utilize molten or fused salt electrolytes.
One such secondary battery utilizes an alkali metal negative reactant, a metal chloride positive reactant which is in contact with a molten alkali metal chloro aluminate electrolyte and a beta alumina derivative separator. This battery is fully described in U.S. Pat. No. 3,877,964 which is assigned to the same assignee as the instant application. The present invention will here be described in most detail in association with the battery of U.S. Pat. No. 3,877,964 since the method in accordance with the invention has been particularly developed for use therewith; however, the method may be utilized in other high-temperature secondary batteries in which the electrolyte or the positive reactions are more sensitive to atmospheric handling than their elemental constituents, or any such battery in which the negative reactant is more sensitive to atmospheric handling than its cations in the electrolyte, or combinations thereof.
2. Description of the Prior Art
It may be explained here that a substantial amount of work has been done in the development of high-temperature secondary electrochemical cells and that the use of molten or fused salts as electrolytes in secondary batteries is not new to the art. Such batteries utilizes as the electrolyte an inorganic salt composition which is solid and non-conducting at ordinary temperatures. However, when the cell is activated by heating it to a temperature sufficiently high to fuse or melt the electrolyte, the molten electrolyte becomes conductive so that electrical energy may be withdrawn from or fed into the cell. Secondary batteries of this type are known for their high energy storage and power output capabilities.
One of the problems associated with batteries utilizing molten or fused salt electrolytes is that generally the positive and negative reactants or the electrolyte or a combination of these constituents making up the batteries are difficult to handle in the production of the batteries because one or more of these materials may react deleteriously with oxygen or moisture in the atmosphere. Thus, controlled atmospheric conditions must be maintained during fabrication of such batteries. For example, in the battery disclosed in U.S. Pat. No. 3,877,964, the constituents making up the battery may comprise a molten sodium negative reactant, an antimony chloride positive reactant, a beta alumina separator and a molten sodium chloroaluminate electrolyte on the positive reactant side of the separator. In the assembly of this battery, a suitable container is filled with sodium metal in the negative reactant compartment and the positive reactant materials or ingredients, in their charged state, are placed in the positive reactant compartment. This means that controlled atmospheric conditions have to be used, that is, no oxygen or water can be present in the atmosphere where the batteries are assembled. Consequently, such batteries must be assembled in glove boxes or other artificial environments having no oxygen or water present in the atmospheres thereof. It can be readily seen that these procedures are not very suitable for large scale production and that they are expensive and time consuming.
Therefore, in view of the above, it is a primary object of the present invention to provide a method for fabricating high-temperature secondary electrochemical cells under substantially ordinary open bench working conditions.
This and other objects and advantages of the present invention will become more apparent in the following detailed description of the preferred embodiment of the invention taken in conjunction with the accompanying drawing.